A Gravitational Lens Candidate Discovered with the Hubble Space Telescope

Abstract

We report evidence for gravitational lensing of the high-redshift (z = 3.8) quasar 1208+101, observed as part of the Snapshot Survey with the Hubble Space Telescope Planetary Camera. An HST V image taken on gyroscopes resolves the quasar into three point-source components, with the two fainter images having separations of 0.1" and 0.5" from the central bright component. A radio observation of the quasar with the Very Large Array at 2 cm shows that, like most quasars of this redshift, 1208+101 is radio-quiet. Based on positional information alone, the probability that the observed optical components are chance superpositions of Galactic stars is small, but not negligible. Analysis of a combined ground-based spectrum of all three components, using the relative brightnesses from the HST image, supports the lensing hypothesis. If all the components are lensed images of the quasar, the observed configuration cannot be reproduced by simple lens models. Future HST observations can test the lensing hypothesis for 1208+101.